PHILADELPHIA, PAEarly life antibiotic exposure was not associated with increased childhood weight gain, reported Jeffrey S. Gerber, MD, PhD, from the Department of Pediatrics, Division of Infectious Diseases, The Children’s Hospital of Philadelphia, Philadelphia, PA, at IDWeek 2014.

Antibiotic exposure has been associated with weight gain in livestock and increased adiposity in experimental animal models, mediated by changes in the gut microbiome. “Infancy and early childhood represent both an influential period of growth trajectory and a time during which antibiotic exposure is common and often inappropriate” noted Dr. Gerber and colleagues. His team aimed to determine the impact of real world, early life antibiotic exposures on childhood weight gain.

The longitudinal, retrospective cohort study included 38,756 children born between 2001 and 2011, who presented for a preventive health visit in the first 14 days of life, and had an additional ≥2 visits in the first year. The children represented a socioeconomically and racially diverse pediatric healthcare network serving >200,000 children at 31 practices. Exclusion criteria included children born <35 weeks gestational age, birth weight <2000g or <5% for gestational age, chronic medical conditions, prophylactic antibiotic use, or frequent steroid use.

Exposures included all systemic antibiotics in the first 6 months of life, and primary outcome was weight through age 8, standardized to WHO/CDC reference populations. The association between standardized weight and age by antibiotic exposure was adjusted for sex, race, insurance type, birth weight, preventive health care compliance, household size, birth year, baseline height and primary care practice site.

A total of 13.7% (5,312) of the 38,756 children included in the analysis received antibiotics in the first 6 months of life. Antibiotic exposure was associated with a significant decrease of 0.03 in weight z-score per year (P<0.001).

A second analysis compared 47 sets of twins, discordant in early life antibiotic exposure, using a longitudinal mixed effects model to assess the association between paired weight difference and age, adjusting for differences in sex, birth weight, and baseline height. Antibiotic exposure was not associated with a significant change in weight in the 47 twin pairs (P=0.59). 

Dr. Gerber and his team were able to conclude that early life antibiotic exposure did not increase early childhood weight in this large birth cohort.